If it is the copper coil it can stay in for 10 years. If it's the Mirena coil it's meant to be in for 5 years. It won't have damaged you but you will have been incredibly lucky not to have fallen pregnant.

Just get it out. You will be fine. Contraception doesn't cause permanent fertility problems, it just masks them.

It will stop working at some point but won't cause any bad effects. I work in a sexual health clinic and we saw a woman a few weeks ago who had had her five year coil in for nine years. Coils also work longer than they say they do because they air on the side of caution but I expect yours is expired now. Just get it changed/ exchanged, no problem

Like a2011x says, it'll be fine. Just have a wee chat with someone who can see your notes from when you had it put in and they will let you know when it should be removed/changed. I work in sexual health too and I have come across spectacularly out of date coils and its usually entirely fine.